After the Apocalypse, people learned to guard from outer world using outer power, thus resulting the Vicious Summoners. They developed a method to resist outer monsters by summoing certain elements from monters? own bodies.

To prevent the repeat of the Apocalypse which resulted from the summoing of outer monsters, they trained themselves to almost immune to anger, sadness and other emotions. And therefore, no matter what kind of treatments they suffer in the communion, they can still concentrate on their missions.